The present invention relates to methods and apparatus for efficiently detecting defective communications lines within a wired communications network.
Most people are familiar with the wired, public telephone network; they have either used telephones connected to that network or seen some of the physical elements making up the network itself, such as aerial cables, buried or underground cables or terminal boxes coupling such cables to houses or other facilities. Virtually everyone is also familiar with the general fragility of the telephone network since most people have experienced a telephone outage caused by trees falling on lines or underground cables damaged by ground shifts or inattentive diggers.
A variety of less obvious and less easily identifiable problems effect the cables that carry telecommunications, internet traffic and data communications through the public telephone network, however. For instance, corrosion at the contact between the telephone cable and a terminal, wear of the insulation surrounding the wires carrying communications, or a wet telephone cable may cause the cables to malfunction. Likewise, lightning can damage the sheath surrounding the cable and wind or water entering the splice between cables can then cause malfunctions. Problems with water entry may be particularly pronounced with older cables, which sometimes were formed using paper insulation surrounded by a lead sheath that was not impervious to water. Moreover, problems may occur even in the more benign environment inside of a building or home. Lint or other material may build within line jacks or interfaces and become sufficiently damp to inject moisture into the lines to cause shorts. Or, insulation on wires running underneath carpet or the like may become worn from constant travel. Stepping near to or on top of worn wires then causes a malfunction.
Often, malfunctions take the form of a low resistance between conductors or a conductor and ground. This is caused by water conducting within the line or a wire carrying power touching a wire that is grounded because of insulation wear or the like.
These problems occur despite extensive measures to protect the many lines that make up a telephone cable. For instance, the typical telephone cable comprises numerous lines. Each line uses a pair of copper (or other) wires. Often the wires are given a slight twist (thus, the name xe2x80x9ctwisted pairxe2x80x9d) in order to minimize interference among the communications signals the wires carry. A cable is made by stranding together several groups of wires to form the cable core. A sheath, comprising layers of aluminum, steel, lead or polyethylene, surrounds the core. The sheath provides electric shielding, water resistance and some armor against blows to the cable. These protections, however, do not always prevent entry of water, insulation wear, corrosion, cuts or other problems from causing shorts.
If the damage to the line causes a permanent short, the defective line is easily identified because it will not work at all. If, however, the short is intermittent, detecting it will be substantially more difficult, if not impossible. Customers may notice some disruption in service and report that to the telephone company. Typically, the company may dispatch a technician to try and identify the problem. Many times the technician will be unable to identify the defective cable pair or the reason for the intermittent failures. Often, it may take several customer complaints and several (expensive) trips before the technician will be able to identify and correct the problem.
Efforts have been made to more proactively identify defective lines. For instance, periodically, switches installed within the network may run an xe2x80x9cALITxe2x80x9d test. The ALIT or xe2x80x9cAutomatic Line Insulation Test,xe2x80x9d may identify some of the lines with permanent breaks or shorts. Telephone companies"" service departments periodically may retroactively analyze trouble reports that record customer complaints or ALIT results to determine whether the cables or xe2x80x9cplantxe2x80x9d in a particular area need to be rehabilitated completely because they have aged and performance has degraded.
Some telephone companies have used a system called the Loop Cable Administration and Maintenance Operations System (called xe2x80x9cLCAMOSxe2x80x9d or xe2x80x9cPredictor systemxe2x80x9d) that is a corputer system that monitors and utilizes information obtained from customer reports, switch messages, and ALIT results to identify trouble areas within the telephone network. The aim of many of the switch messages received by the Predictor system is to provide information that helps protect the telecommunications switches from overload or other negative conditions. Thus, thresholds may be set such that intermittent pulses are not viewed as a triggering event that would cause the system to identify a particular cable pair or, more likely, a group of cables, as having a problem. The Predictor system reportedly correlates this data with other information so that lines with trouble messages will be tested automatically when they fall within limits of preset thresholds. Also, the Predictor system can issue reports indicating problems developing in the telephone network depending on thresholds set by the user in order to control the flow of information appearing on the report.
However, neither ALIT nor the Predictor system properly identifies particular lines or cables that are generating intermittent shorts or pulses. Dealing with these intermittent pulses by dispatching technicians every time a customer calls is very expensive. The intermittent problems or pulses may additionally prevent telephone companies from offering valuable xe2x80x9cN11xe2x80x9d services. xe2x80x9cN11xe2x80x9d services are those in which telephone users can dial a xe2x80x9cN11xe2x80x9d number, where N is a number from 2 to 9, and be automatically routed to one point within the telephone network. The most familiar such service in North America is the emergency 911 service, through which telephone users can immediately contact emergency services such as police, fire or ambulance units.
Many telephone companies, however, would also like to offer other N11 numbers to their clients. For instance, BellSouth Telecommunications, Inc. has offered 211 service to United Way. Anyone dialing 211 throughout a particular area, such as metropolitan Atlanta, Ga., would be immediately routed to United Way""s customer calling center. Other N11 services have been contemplated or offered, including 411 service to provide telephone information; 511 service for commercial information; or 611 service for repairs.
Pulse dialing, also known as rotary dialing, interrupts the telephone line current with a series of breaks or xe2x80x9cclicksxe2x80x9d that are essentially shorts and opens on the line. By changing the number of breaks (or pulses) in the string over a preset period, the number being dialed can be changed. The telephone switch is designed to recognize dial pulses at the standard rate of 10 pulses per second and may recognize pulses well outside that range. If there is a single pulse, the number being dialed is xe2x80x9c1xe2x80x9d; if ten pulses occur, the number being dialed is xe2x80x9c0.xe2x80x9d Offering 211 and other N11 services where xe2x80x9cNxe2x80x9d is a smaller number results in generation of many spurious calls by defective telephone lines that effectively dial the N11 number by means of the intermittent shorts and opens in the line caused by the defects mentioned above. These shorts and opens, which temporarily interrupt line current, may be viewed by network switches as pulse dialing signals, which the network switches interpret as actual calls by customers if the pulses are grouped and timed to resemble an actual number. Switches filter out many of these pulses, e.g., a pulse that generates a single digit, like 1, 2 or 3, or several series of pulses that generate a set of numbers less than three, like 21, 32 or 11, simply because switches are not designed to recognize those numbers as legitimate calls. But because switches are biased to complete telephone calls once they receive the correct number or set of digits, a defective communication line can generate a N11 number that is recognized by the switch and routed to any destination associated with the N11 number.
The frequency of such improperly dialed numbers declines as the xe2x80x9cNxe2x80x9d in the N11 service increases in value. Thus, spurious calls to a 911 number are less frequent than spurious calls to a 211 number. That simply reflects that it is less probable that a defective line will generate the required pattern of pulses to dial 911 than 211. Conceivably, a defective line could also dial other telephone numbers, although the statistical probability drops as the number of required pulses per digit and number of digits per phone number increase. Thus, while it is possible that a 222 number could be dialed, it is less likely that a defective cable could generate the pulse combinations needed to dial a 7 digit phone number.
In any event, experience has shown that the N11 numbers using lower digits like 2, 3 or 4 will generate numerous spurious calls because of the existence of defective communications lines. For example, after a particularly bad storm in one area in which 311 service was being offered to connect customers to emergency medical services, hundreds of spurious calls were generated, probably because the storm caused water to enter cables that then shorted out intermittently the communications lines, thereby generating pulses necessary for the line to effectively dial the 311 number.
Unfortunately, such calls cannot be screened out given the chance that a legitimate call may be initiated to the possibly critical (in the case of emergency services) number. The best solution is to identify and correct defective communications lines. The present methods for detecting intermittently defective communications lines are inadequate and expensive. A need accordingly exists for efficiently and quickly detecting defective cable pairs in order to correct the problems with the line and allow quality offerings of N11 or similar services using a limited number of digits that are in the lower ranges of value.
The present invention overcomes the above problems by providing methods for detecting, logging, analyzing and testing defective communications lines and, in particular, detecting lines only intermittently defective. Generally detection methods may be implemented that passively monitor for and identify signals generated by defective communications line. For example, one method involves detecting spurious communications and associating those communications with the defective communication lines that generated each particular communication. This method can be implemented in non-switched based solutions. This allows quick, efficient implementations of the method without the need for extensive reconfiguring or reprogramming of the switch by the switch manufacturer. Alternative methods for using a central office switch to monitor and identify signals symptomatic of defective communication lines are also disclosed. Such methods allow not only for more efficient detection, but may be automated and used to collect data that allows further analysis of the lines and communications network itself.
The method of the present invention aims to detect signals indicating a possible defect in a communications line. Those signals are then correlated with the line generating them. Thus, defective communications lines, which include wires, twisted pair wires and the like, are identified by recognizing spurious communications from these lines and associating them with the particular line from which they originated. xe2x80x9cSpurious communicationsxe2x80x9d means a communication, attempted communication or other signal intermittently. generated by a defective communications line rather than by a user attempting to access the services provided via the communications line. By way of example, the defective communication line generates the spurious communications by shorting or otherwise seizing the line to effectively dial a digit or series of digits.
The detection step may be implemented by, for instance, defining an N11 or other selected telephone number to which all communications in a given area are routed by network switches. Defective communications lines will generate without user intervention pulses that pulse dial the selected number. Analyzing the pattern of calls to the selected number or listening to each call received by the selected number will identify whether the communication pulses are spurious and the line therefore is defective or whether the user of the line purposefully dialed the calls. Thus, the call pattern from a particular line can be analyzed to determine whether the calls are coming at odd hours and during conditions suggesting the line is defective. For instance, if the same line generates multiple calls to the chosen N11 number late at night or during inclement weather, chances are high that the line is defective and the defects are essentially causing the line to dial pulses. Alternatively, a device may physically monitor the line after a call to determine the presence of either frequencies suggesting only noise is on the line (indicating a defective line made the call) or frequencies suggesting the line carries human voice or data (indicating a user initiated the call). Either or a combination of these analyses determine whether the pulses dialed and resulting communication are, in fact, spurious.
Once a spurious communication has been identified, the communication is associated with a particular communication line. This association step may be performed by determining the originating telephone number generating the spurious call. That originating number is associated with a particular communications line; alternatively, a switch may be programmed to identify the originating equipment associated with the particular line that generated the spurious communication.
The methods of the present invention may be implemented with very few changes to the switches within a communications network. Thus, in one embodiment of the invention, switches may be configured simply to route N11 or other calls to an intercept platform. The intercept platform collects and logs call data, including the originating number, date/time, etc. of each incoming call. The logged information can be manually reviewed in order to determine which of the calls appear to be spurious and confirm their association with a particular communications line. Alternatively, the logged information can be logged into a database for automated processing and analysis.
Reprogramming the switch allows for a broader range of spurious pulses to be detected. For instance, in an alternative configuration, a central office switch may be reconfigured to detect spurious communications caused by pulses generated by defective communication lines without the need to route N11 or other calls to an intercept platform. Or, the switch can detect spurious pulses or other signals that are symptomatic of a defective line. Switches may be reprogrammed to detect the following spurious pulses: line seizures involving incompletely dialed pulses; line seizures involving pulses that do not fall within published standards for dialing pulses; line seizures involving pulses that are of unequal amplitude or whose amplitudes are not typical of that particular line; or line seizures involving pulses from lines that normally use DTMF dialing. In short, detection flexibility can be greatly expanded with firmware changes within the central office switches.
Additional programming changes allow the switch to log detected discrepancies into a database for further processing by the switch or an external device. For instance, individual switches may be configured to collect data for a certain time frame and then forward it to a master database coupled to a workstation that allows further processing and analysis. The analysis may include reviewing forwarded call detail records in order to identify spurious calls based upon identification of atypical calling patterns. Additionally, multiple spurious communications may be correlated with the geographic areas from which they each originate. Areas having a high percentage of spurious communications will inform network outside plant engineers of the possible need to update the entire plant in that geographic area or take other remedial or preventive measures to preclude further service interruptions.
The present invention accordingly aims to achieve at least one or combinations of the following objectives:
To provide a method for detecting intermittently defective communications lines within a communications networks.
To passively detect such defective communications lines by monitoring for and identifying signals symptomatic of such lines and correlating the symptomatic signals with the originating line.
To detect spurious calls generated by defective communications lines.
To detect spurious calls by determining that a particular defective communication line generated a pulse.
To detect spurious calls by analyzing calls made to a selected N11 or other low digit and set value telephone number.
To associate detected spurious calls with the defective communications line generating those calls.
To provide improved N11 services by efficiently detecting defective communications lines and thereby decreasing disruptive, illegitimate calls to the N11 service center.
To provide methods for automatically analyzing switch events in order to detect intermittently defective communications lines.
Other objects, features and advantages of the present invention will become apparent upon reading the rest of this document.